The invention relates generally to semiconductor device fabrication and, in particular, to methods of fabricating stress sensors and sensor integrated circuits incorporating one or more nanowire field effect transistors, as well as methods of sensing stress using one or more nanowire field effect transistors.
The electrical detection of mechanical stress is critical in many applications, such as measuring an external force applied to an object. Knowledge of mechanical stresses may be used as a factor in the electronic device phase to predict the performance of an integrated circuit. As another example, a packaging process may be modified to mitigate excessive mechanical stresses. Conventional analog complementary metal-oxide-semiconductor (CMOS) stress sensors have been proposed and used for stress sensing. A typical conventional stress sensor relies on the piezo-resistive performance of metal-oxide-semiconductor field effect transistors (MOSFETs). Of course, another solution for the electrical detection of mechanical stress is the use of a conventional strain gauge.
When die are mounted and packaged, mechanical stresses are inherently introduced into the die package and additional mechanical stresses are introduced during integrated circuit operation. Moderate mechanical stresses may impair the electrical performance of the integrated circuit. At higher mechanical stresses, the integrated circuit may experience a partial or complete failure of functionality that is reversible. Further increases in the mechanical stress applied to the semiconductor material of the die may initiate a crack, which may propagate and result in fracture. If cracking or fracture occurs, the resultant damage to the integrated circuit is likely irreversible.
Components fabricated with the emerging technologies of microelectromechanical systems (MEMS) are being incorporated in an increasing number of consumer applications including, but not limited to, automotive electronics, medical equipment, cell phones, hard disk drives, computer peripherals, and wireless devices. In MEMS technologies, mechanical elements, sensors, actuators, and electronics are integrated on a common silicon substrate through microfabrication technology.
Methods for fabricating stress sensors and stress sensor circuits, as well as methods for sensing mechanical stress, are needed that overcome the disadvantages of conventional fabrication methods and stress sensing methods for these types of devices and circuits.